I have been trying to get a usb cdc example app up and running on the
stm32f103. My attempt has been adapted from the example at:
https://github.com/libopencm3/libopencm3-examples/blob/master/examples/stm32/f3/stm32f3-discovery/usb_cdcacm/cdcacm.c
with appropriate changes for the f103 initialization.
The problem is that it hangs very early in the usbd_init() routine. I
copied the libopencm3 file usb_f107.c into my local project directory and
instrumented it with some blink(x) calls to find the point of the hang:
/** Initialize the USB device controller hardware of the STM32. */
static usbd_device *stm32f107_usbd_init(void)
{
rcc_periph_clock_enable(RCC_OTGFS);
/* Control gets to here ok.. */
blink(2);
/* And then hangs here.. */
OTG_FS_GUSBCFG |= OTG_GUSBCFG_PHYSEL;
blink(3);
/* Wait for AHB idle. */
while (!(OTG_FS_GRSTCTL & OTG_GRSTCTL_AHBIDL));
The program starts up ok, and initializes a number of things before calling
usbd_init(). I get as far as the blink(2) call (above), but it hangs
thereafter. If I comment out the OTG_GUSBCFG_PHYSEL statement, it simply
hangs at the "Wait for AHB idle" loop.
I did a lot of guesswork for clock setup etc. so there is likely a lot more
here than is necessary:
int
main(void) {
int x;
usbd_device *usbd_dev;
rcc_clock_setup_in_hse_8mhz_out_72mhz();
rcc_set_usbpre(RCC_CFGR_USBPRE_PLL_CLK_DIV1_5); // 48 MHz
rcc_periph_clock_enable(RCC_GPIOA);
rcc_periph_clock_enable(RCC_GPIOC);
rcc_periph_clock_enable(RCC_APB1ENR); // Needed?
rcc_periph_clock_enable(RCC_APB2ENR); // Needed?
rcc_periph_clock_enable(RCC_APB2ENR_AFIOEN); // Needed?
rcc_periph_clock_enable(RCC_AHBENR_OTGFSEN);
rcc_periph_clock_enable(RCC_AHBENR_CRCEN);
rcc_periph_clock_enable(RCC_CRC);
rcc_periph_clock_enable(RCC_USB);
gpio_set_mode(GPIOA
,GPIO_MODE_OUTPUT_50_MHZ,GPIO_CNF_OUTPUT_PUSHPULL,GPIO11);
gpio_set_mode(GPIOA,GPIO_MODE_OUTPUT_50_MHZ,GPIO_CNF_OUTPUT_PUSHPULL,GPIO12
);
gpio_set_mode(GPIOC,GPIO_MODE_OUTPUT_2_MHZ,GPIO_CNF_OUTPUT_PUSHPULL,GPIO13);
// LED
blink(5);
led(1); /* ok so far.. */
usbd_dev = usbd_init(&stm32f107_usb_driver,&dev,&config,
usb_strings,3,
usbd_control_buffer,sizeof(usbd_control_buffer));
/* Control never comes back here.. */
blink(3);
The fact that it hangs suggests maybe that I am leaving a clock disabled.
The few examples that I did find did barely performed any setup and purport
to have a working example (or at least for that time). Hopefully someone
can point out some obvious problem. I'm running out of ideas.
The full source code is here:
https://github.com/ve3wwg/stm32f103c8t6
in subdirectory rtos/usb1. While this project is built as a FreeRTOS
program, it is not using any task scheduling etc. at this time.
Just type "make" at the ./rtos/usb1 level to build it (it does however
require that the libopencm3 project be available and built at top-level
./libopencm3 however).
Thanks, Warren
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